ML12341A129

E-mail, Draft Request for Additional Information, Round 2, Request to Revise Technical Specifications to Eliminate Use of the Term Core Alteration Consistent w/TSTF-471 and NUREG-1432, Rev. 3 (TAC ME8160/ME8162)

ML12341A129
Person / Time
Site:	Palo Verde
Issue date:	12/05/2012
From:	Lauren Gibson Plant Licensing Branch IV
To:	Roehler R Arizona Public Service Co
Gibson L
References
TAC ME8160, TAC ME8161, TAC ME8162
Download: ML12341A129 (3)

Text

Lent. Susan From: Gibson, Lauren Sent: Wednesday, December 05, 201211:13AM To: Robert. Roehler@aps.com

Subject:

Draft Request for Additional Information Related to LAR to remove the term CORE ALTERATION from Tech Specs (ME8160, ME8161, and ME8162)

Attachments: Draft RAls ME8160, 1, 2.docx

Rob, a dated March 8, 2012, and supplemented by letter dated October 11, 2012) Arizona Public Service Co, (APS. the licensee) submitted a license amendment (LAR) for Palo Verde Nuclear Generating Station (Agencywide Documents Access Management System (ADAMS) /"ccession No. ML12076A045 and ML12286A330, respectively), The proposed amendment would the use of the term CORE ALTERATION from the technical specifications.

The U.S, Nuclear Regulatory Commission (NRC) staff has reviewed the information provided by the licensee and determined that the additional information identified in the attachment is needed in order for the NRC staff to complete review.

Please contact me jf you would like to have a clarifying conference call.

Thank you, Lauren Lauren K Gibson Project Manager Columbia Generating Station Palo Verde Generating Station of Operating Reactor Licensing Nuclear Commission 1

DRAFT REQUEST FOR ADDITIONAL INFORMATION REGARDING REMOVAL OF "CORE ALTERATION" FROM TECHNICAL SPECIFICATIONS (TSS) INCLUDING TS 3.9.2. "NUCLEAR INSTRUMENTATION" FOR PALO VERDE NUCLEAR GENERATING STATION (PVNGS), UNITS 1. 2. AND 3 DOCKET NOS. 50-528. 50-529 AND 50-530 Request for Additional Information By letter dated March 8, 2012, supplemented by a letter dated October 11,2012, Arizona Power Service Company (APS), the licensee for Palo Verde Nuclear Generating Station (PVNGS),

Units 1,2, and 3, proposed to remove "CORE ALTERATION" from Technical Specifications (TSs) including TS 3.9.2, "Nuclear Instrumentation".

The NRC staff has reviewed the submitted information and has determined that the following additional information is required to complete the review.

1. For Palo Verde Nuclear Generating Station (PVNGS), current Technical Specification (TS) 3.9.2 (for Mode 6), "Nuclear Instrumentation", requires that (1) Core Alterations be suspended and (2) positive reactivity activities be terminated if the required source range nuclear instrumentation is determined to be inoperable. The licensee proposes to remove the required action of suspending Core Alterations from the TS 3.9.2 while maintaining the required action of suspending positive reactivity activities.

At PVNGS, the source range monitors (SRMs) are used during refueling operations to monitor the core reactivity conditions. The SRMs provide a signal to operator of unexpected changes in core reactivity such as a boron dilution event and a misloaded fuel assembly event. These detectors are located external to the reactor vessel and detect neutron leaking from the core. The licensee stated in References 1 and 2 that for the conditions that one SMR is inoperable, the required action of suspending positive reactivity additions is sufficient to preclude an accident criticality.

Based on the current definitions in TS 1.1, "CORE ALTERATION shall be the movement or manipulation of any fuel, sources, or reactivity control components [excluding control assemblies (CEAs) withdrawal into the upper guide structure], within the reactor vessel with vessel head removed and fuel in the vessel. Suspension of CORE ALTERATIONS shall not preclude completion of movement of a component to a safe position".

With the removal of the TS required action of suspending CORE ALTERATION, the only TS 3.9.2 restriction is the required action to suspend positive reactivity operations.

Since the withdrawal of fuel assemblies from the core may not contribute to the addition of positive reactivity to the core, it is not prohibited by the proposed TS 3.9.2.

The NRC staff is concerned that the SRM could be decoupled from the nuclear response when the fuel assemblies are withdrawn out of the core. For example, the withdrawal of fuel assemblies could result in a condition where fuel assemblies reside in a half of the

core opposite the operable SRM. Another example is removal of a source assembly from a decayed core. Under these conditions, the remaining operable SRM may not be able to effectively detect the neutron reactivity. Thus, there may not be an SRM to adequately detect the occurrence of the boron dilution or misloaded fuel assembly event, resulting in an unanalyzed condition.

a. Please address whether the operable SRM could be decoupled from the neutron fluxes during a fuel assembly withdrawal in Mode 6.

b. If the SRM-neutron decouple is determined to be a non-credible phenomenon, provide rationale in support of the determination.

c. If the SRM-neutron decouple is determined to be a credible phenomenon, justify the proposed change to remove CORE ALTERATION from the TS. The justification should include information addressing the compliance with:

i. Acceptance criterion in Standard Review Plan (SRP) 15.6.4 that requires that at least 30 minutes is available from the time the operator is made aware of the unplanned boron dilution event to the time a total loss of shutdown margin (criticality) occurs during refueling (Mode 6), and ii. Guidance of Item 4 on page 15.4.6-8 of SPR 15.6.4 (Revision 2 dated March 2007) that specifies that redundant alarms should be available for the operator to identify and terminate the unplanned boron dilution within the required time

2. The NRC staff is concerned that without a prior criticality analysis, it could be difficult to tell whether shuffling an assembly (change the core geometry) causes a positive or negative reactivity change. By restricting core alteration, rather just positive reactivity addition, current TS 3.9.2 explicitly delineates components that cannot be moved, and this TS restriction of core alteration could prevent the operator from misjudging the reactivity of the fuel assembly movement.

Please describe how the licensee determines whether shuffling an assembly would cause a positive or negative reactivity change.